The subject matter discussed in this section should not be assumed to be prior art merely as a result of its mentioned in this section. Similarly, a problem mentioned in this section or associated with the subject matter provided as background should not be assumed to have been previously recognized in the prior art. The subject matter in this section merely represents different approaches, which in and of themselves may also correspond to implementations of the claimed technology.
Various imaging devices with depth-sensing capabilities include two (or more) cameras and, optionally, one or more light sources to illuminate a scene and thereby enhance contrast between foreground and background objects. The relative positions and orientations of the two cameras and of the lens and image sensor within each camera, as well as the shapes of the two lenses, are generally fixed by design in accordance with specified parameters. Knowledge of these parameters facilitates, at least in principle, determinations of the spatial position (including depth) of objects within the fields of view of both cameras from two images simultaneously taken therewith.
However, due to the inherent variability of any manufacturing process, the actual parameters usually deviate slightly from the nominal design parameters and vary from device to device, limiting the accuracy and/or precision of the determinations. To improve accuracy and precision, each individual motion-capture device is, therefore, typically calibrated following manufacture to determine the actual values of the design parameters; these may then be taken into consideration when computing positions and tracking motions based on images acquired by the cameras. Calibration may be performed at the manufacturing facility, and generally involves acquiring images of an object or pattern of known dimensions (e.g., a checker-board pattern of known unit size) with both cameras, and computing a set of parameters reflecting the deviation from expected parameter values—e.g., by minimizing a metric of the difference between the actual images and the theoretically expected images as derived from the known dimensions and the parameter values.
While the motion-capture device generally yields accurate positional determinations immediately upon calibration and for some time thereafter, the performance may deteriorate over time as the parameter values change as a consequence of, e.g., temperature fluctuations and/or mechanical forces to which the device may be subjected during use or transport. Consequently, there is a need for improved techniques affording re-calibration of the device by the end-user.